Electrostatic discharge device integrated with pad

ABSTRACT

A structure of an electrostatic discharge (ESD) device integrated with a pad is provided. The ESD device is integrated with the pad and formed under the pad. By using the area under the pad, the ESD device does not occupy additional space of an integrated circuit. Furthermore, since the pad is a large, plate, and ideal conductor, the connected pad and the ESD device are capable of distributing current in the ESD device averagely.

FILED OF THE INVENTION

The present invention relates to an electrostatic discharge (ESD) device and more particularly, to an ESD device integrated with pad.

BACKGROUND OF THE INVENTION

ESD devices have been widely used in integrated circuits to prevent damages from electrostatic voltage. Generally, the ESD devices occupy substantial space in an integrated circuit, which increases the manufacturing cost. Furthermore, conventional ESD devices are generally located near the pads horizontally. The dimension of the ESD devices is generally large and the current flowing characteristic of the conducting wire, such as metal, is not ideal. This could causes that the current flowing through the ESD device is not average. Moreover, this may affect the electric character and reduce breakdown endurance of the ESD device.

Therefore, an ESD device with reduced essential space and improved electric character is desired.

SUMMARY OF THE INVENTION

According to one aspect of the invention, an ESD device is integrated with a pad. Based on in-between voltage variation of complementary polar region, the ESD device can protect an integrated circuit from being damaged by electrostatic voltage.

According to another aspect of the invention, an ESD device is integrated with the pad and formed under the pad. By using the area under the pad, the ESD device does not occupy additional space of the integrated circuit.

According to another aspect of the invention, an ESD device is integrated with the pad and formed under the pad. Since the pad is a large and plate conductor, the connected pad and the ESD device can distribute the current in the ESD device averagely.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the embodiments of the present invention taken in conjunction with the accompanying drawings.

FIG. 1 shows a cross-sectional diagram according to one embodiment of the present invention.

FIG. 2 shows a cross-sectional diagram according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to exemplary implementations, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The following examples and implementations overcome the disadvantages of the conventional ESD devices and are able to reduce the size and cost of the integrated circuit. According to one example, ESD devices are formed under a pad, and connected to the pad with metal. Since the pad is a conductor, the current flowing from the pad to the ESD devices is well distributed, which improves the performance of ESD devices.

To form the ESD devices under the pad saves the cost and substantial die space in IC manufacturing. The ESD devices make use of in-between voltage variation of complementary polar region. In other words, the ESD devices can prevent damages from electrostatic voltage by breakdown mechanism between N-type doping region and P-type substrate or, in another example, P-type doping region and N-well.

FIG. 1 illustrates a cross-sectional view diagram of an ESD device 100 integrated with a pad metal layer 308 in one embodiment of the present invention. The ESD device 100 uses in-between voltage variation of an N-well 106, an N+ region 104 b and a P-type substrate 102 to form a junction breakdown mechanism. When electrostatic voltage reaches a predetermined value, the ESD device 100 discharges the electrostatic voltage via the junction breakdown mechanism to protect the integrated circuit.

The ESD device 100 includes an anode 302 and a cathode 304. The anode 302 is directly connected to the pad metal layer 308 with a via 306. This makes the connection between the ESD device 100 and the pad metal layer 308. The anode 302 connects an N+ region 104 a and two P+ regions 202 a together. The cathode 304 connects two N+ regions 104 c and a P+ region 202 b together.

The ESD device 100 does not need extra mask of a standard CMOS process or similar process. Generally, area under the pad is spacious enough to contain the ESD device 100. Moreover, this ESD device structure may be poly-free and the structure combining an ESD device and a pad is also suitable in complementary process.

FIG. 2 shows a cross-sectional view diagram of an ESD device 1100 integrated with a pad metal layer 1308 in another embodiment of the present invention. The ESD device 1100 also has a P-type substrate 102. The ESD device 1100 further includes an NBL (N-type Buried layer) 101 formed in the P-type substrate 102. An anode comprises an N+ region 1204 b and two P+ regions 1102 c. A cathode comprises two N+ regions 1204 a and a P+ region 1102 a. The cathode is connected to a pad metal layer 1308 by a via 1306.

The ESD device 1100 mainly uses in-between voltage variation of a P-well 1108, a P+ region 1102 b and an N-well 1106 to form a junction breakdown mechanism. When the electrostatic voltage reaches a predetermined value, the ESD device 1100 discharges the electrostatic voltage via the junction breakdown mechanism to protection the integrated circuit.

While embodiments of the present invention are illustrated and described, various modification and improvement can be made by those skilled in the art. The embodiment of the present invention is therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated. And all the modification maintaining the spirit and realm of the present invention are within the scope as defined in the appended claims. 

1. A structure of an electrostatic discharge device integrated with a pad, said structure comprising: a P-type substrate; an N-well, formed in said P-type substrate as a part of said electrostatic discharge device; at least one first N+ region formed outside said N-well, said first N+ region being isolated from said N-well and regions herein, and other doped regions in said P-type substrate by field oxides; at least one first P+ region formed outside said N-well, said first P+ region being isolated from said N-well and regions herein, other doped regions in said P-type substrate, and said first N+ region by field oxides; at least one second N+ region formed inside said N-well; at least one second P+ region formed inside said N-well; a first electrode, connecting at least one second N+ region with at least one second P+ region via an electric conductor, which comprises metal; a second electrode, connecting said first P+ region with said first N+ region via another electric conductor, which comprises metal; and a pad, formed on the top of said structure.
 2. The structure as claimed in claim 1, wherein said pad is connected to said first electrode, wherein said second electrode is designated to be connected to a voltage level, comprising power supply voltage or ground, via an electric conductor, which comprises metal.
 3. The structure as claimed in claim 1, wherein said pad is connected to said second electrode, wherein said first electrode is designated to be connected to a voltage level, comprising power supply voltage or ground, via an electric conductor, which comprises metal.
 4. The structure as claimed in claim 1, wherein said second N+ region and said second P+ region are formed next to each other.
 5. A structure of an electrostatic discharge device integrated with a pad, said structure comprising: a P-type substrate; an N-type buried layer, formed in said P-type substrate; an N-well, formed on said N buried layer as a part of said electrostatic discharge device; a P-well formed on said N buried layer next to said N-well; at least one third N+ region formed inside said N-well, said third N+ region being isolated from said P-well and regions herein, and other doped regions in said N-well by field oxides; at least one third P+ region formed inside said N-well, said third P+ region being isolated from said P-well and regions herein, other doped regions in said N-well, and said third N+ region by field oxides; at least one fourth N+ region formed inside said P-well; at least one fourth P+ region formed inside said P-well; a first electrode, connecting at least one fourth N+ region with at least one fourth P+ region; a second electrode, connecting said third P+ region with said third N+ region; and a pad, formed on the top of said structure.
 6. The structure as claimed in claim 5, wherein said P-well is structurally formed in response to the formation of said N-type buried layer and said N-well.
 7. The structure as claimed in claim 5, said P-well being formed by doping P-type ions.
 8. The structure as claimed in claim 5, wherein said pad is connected to said first electrode, wherein said second electrode is designated to be connected to a voltage level, comprising power supply voltage or ground, via an electric conductor, which comprises metal.
 9. The structure as claimed in claim 5, wherein said pad is connected to said second electrode, wherein said first electrode is designated to be connected to a voltage level, comprising power supply voltage or ground, via an electric conductor, which comprises metal.
 10. The structure as claimed in claim 5, wherein said fourth N+ region and P+ region are formed next to each other. 